This paper describes the development and verification of a fracture criterion sensitive to the elastic-plastic behavior of asphalt concrete mixes. This method is based on the elastic-plastic fracture mechanics (epfm) concept that leads to the laboratory determination of the critical strain energy release rate, also called the criticalvalue of j integral, j sub 1c. Also employed was the linear elasticfracture mechanics approach (lefm), which leads to the determination of critical stress intensity factor, also called fracture toughness, k sub 1c. Asphalt concrete beams 3 in. By 3 in. By 16 in. Were tested under three-point bending. Notches 1/16 in. Wide and long enough so that the ratio of notch depth to beam depth always remained between 0.5 And 0.7 Were sawed at the midpoint of the beams to give a single-edge notch beam geometry. A locally used mix design called id-2 was employed. Twelve asphalt cements were selected from around thecountry for making the mixes. Testing was conducted at four temperatures below 60 deg f (16 deg c): -5 deg f (-21 deg c), 10 deg f (-12deg c), 25 deg f (-4 deg c), and 40 deg f (4.0 Deg c). Both epfm and lefm approaches were used to analyze the laboratory data. The results were compared with the more routine tests, such as indirect tensile strength for aspahlt mixes, as well as the fraass brittle point test, t sub pen1.2, And t sub g from dsc and dma for asphalt cement.It was found that at low temperatures (below 60 deg f (16 deg c)) the epfm approach with j sub 1c as a fracture characterization parameter is sensitive to asphalt mix properties. J sub 1c also seems to be related to the routine parameters. Lefm with k sub 1c as a fracture characterization parameter is not sensitive to asphalt grade or source. This paper appears in transportation research record no. 1228, Asphalt mixtures and asphalt chemistry.
Abstract